This invention relates to apparatus for removing dust from seriform substances.
An object of the present invention is to provide apparatus for removing dust from aeriform substances, especially hot air.
With this object in view the present invention provides apparatus for the removal of dust from aeriform substances characterised in that in it the removal of the dust takes place by intimate and total mixing of the aeriform substance laden with dust with water and the spontaneous passage of the dust into the water with liberation of the cleansed aeriform substances. A plant of the present invention comprises at least one water jet pump, an aspirating mouth connecting to the aeriform substance required to have the dust removed therefrom, at least one decantation tank connecting with the pressing mouth of said water jet pump, at least one pump connecting with its respective aspirating mouth to the said decantation tank at a height greater than the sludge/water interface a hydraulic circuit for connecting the pressing mouth of said last pump with the ejectors of the water jet pump, thus re-cycling it in order to make it act again as a propulsive medium for the dusty aeriform substance and to pick up the relative dust, and means for removing from the tank the decanted sludge and dispatching it for disposal or for recovery.
A Bunsenpump is, in the present state of the art, generally used as an instrument for laboratory tests with only small quantities of air. The use of such a pump in industrial plants for pumping quantities of air of the order of a million m.sup.3 /hour has required specific improvements to be made to the simple and conventional geometrical structure of the pump, especially as the desired action of the pump on the aeriform substance is basically an aspirating action; as for the propelling water, it can consume substantially all the kinetic energy in the intake of the air being collected through fall in the decantation tank. And more than that, this fall is, itself, of aid in the processes of aspiration.
This plant is particularly but not exclusively used for the removal of dust from the hot and powdery airs and gases of cement works, incinerators and the like.
The apparatus can remove nearly all the dust from dustladen airs, and all the dust which is collected in the form of sludge in the decantation tank can be recycled, where, of course, it proves economic to do so; this is precisely the case in cement works where the sludge can be recycled as raw material.
In a cement works plant, dust is a major problem and this dust is found in a variety of locations, for example, the extraction site, the crushing site, the site at which the raw material is ground up, the mixing site, the cooling site, and at the storage site for the raw material. In all these sites apparatus of the type which form the object of the present invention, can be profitably put into use. In the cooling site, the apparatus of the present invention probably constitutes the only dust removal apparatus known at present which can be used at such a site. In fact, at such a site, there are gases at a temperature of about 1300.degree. C. which emerge dusty at a temperature of about 500.degree. C. which are then fed to a discharge chimney.
In the present state of the art, cement works are generally confined to using two types of filters. A first type of filter generally used is one made of textile fibres which, for the purposes of the dust removal, is excellent but which cannot be used at temperatures higher than 300.degree.. A second type of filter generally used is an electrostatic one. Electrostatic filters are relatively costly and their operations are limited by the fact that the gases to be treated may have to be at temperatures and humidities which are conditioned and constant. Hence, the use of such filters and other conventional filters, downstream of the furnace of a cement works at the cooling site is generally impractical. On the other hand, such sites produce a considerable amounts of dust which, when admitted into the atmosphere, may spread for miles and miles causing substantial damage to the environment. If this dust is, however, collected and transformed into sludge by the apparatus of the invention, the dust can be recycled and substantial economies achieved.
The apparatus of the present invention is particularly suitable for such sites not only because it may be indispensable but also because of its simplicity, for its economy of operation and because it brings about a substantially total removal of the dust from the air, allowing the dust to be recycled.
In fact, the apparatus of the present invention effects a substantially total recovery not only of the dust in the air and the operating water used in the apparatus, but also of the very same energy used to pump the water because the water, still in accordance with the present invention, is used to transform the energy to provide an air recycling system which, in any case, would have to be provided by the use of energy in a machine specifically designed for such a purpose.
As a rule, the apparatus performs in a relatively simple manner and this simplicity of operation means that the desired characteristics of the apparatus can be chosen and determined at will by simply assembling together the appropriate number of operating units. The actual operating characteristics of the apparatus can be determined with a wide degree of freedom.